U.S. patent application number 14/034240 was filed with the patent office on 2014-01-23 for methods of conditioning a planarizing pad.
This patent application is currently assigned to MICRON TECHNOLOGY, INC.. The applicant listed for this patent is MICRON TECHNOLOGY, INC.. Invention is credited to Naga Chandrasekaran, Arun Vishwanathan.
Application Number | 20140024297 14/034240 |
Document ID | / |
Family ID | 38575874 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140024297 |
Kind Code |
A1 |
Chandrasekaran; Naga ; et
al. |
January 23, 2014 |
METHODS OF CONDITIONING A PLANARIZING PAD
Abstract
Processing pads for mechanical and/or chemical-mechanical
planarization or polishing of substrates in the fabrication of
microelectronic devices, methods for making the pads, and methods,
apparatus, and systems that utilize and incorporate the processing
pads are provided. The processing pads include grooves or other
openings in the abrading surface containing a solid or partially
solid fill material that can be selectively removed as desired to
maintain the fill at an about constant or set distance from the
abrading surface of the pad and an about constant depth of the pad
openings for multiple processing and conditioning applications over
the life of the pad.
Inventors: |
Chandrasekaran; Naga;
(Boise, ID) ; Vishwanathan; Arun; (Boise,
ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MICRON TECHNOLOGY, INC. |
Boise |
ID |
US |
|
|
Assignee: |
MICRON TECHNOLOGY, INC.
Boise
ID
|
Family ID: |
38575874 |
Appl. No.: |
14/034240 |
Filed: |
September 23, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13469524 |
May 11, 2012 |
8550878 |
|
|
14034240 |
|
|
|
|
11400707 |
Apr 6, 2006 |
8192257 |
|
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13469524 |
|
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Current U.S.
Class: |
451/56 |
Current CPC
Class: |
B24B 53/017 20130101;
B24B 37/26 20130101 |
Class at
Publication: |
451/56 |
International
Class: |
B24B 53/017 20060101
B24B053/017 |
Claims
1. A method of conditioning a planarizing pad, comprising:
conditioning a pad surface of a planarizing pad comprising: a pad
structure comprising: a pad material surface; and openings
extending into the pad material from the pad surface; and a
partially solidified fill material partially filling the openings,
and comprising: a flowable and curable portion; and a solidified
portion over the flowable and curable portion within the openings;
and removing a portion of the partially solidified fill material
from the openings to a distance from the pad surface of the pad
material; and solidifying another portion of the partially
solidified fill material.
2. The method of claim 1, wherein conditioning a pad surface of a
planarizing pad comprises at least one of abrading and buffing the
pad surface of the planarizing pad.
3. The method of claim 1, wherein conditioning a pad surface of a
planarizing pad comprises contacting the pad surface of the
planarizing pad with a conditioning pad.
4. The method of claim 3, wherein contacting the pad surface of the
planarizing pad with a conditioning pad comprises: rotating the
conditioning pad; and contacting the pad surface of the planarizing
pad with the rotating conditioning pad while rotating the
planarizing pad.
5. The method of claim 3, wherein contacting the pad surface of the
planarizing pad with a conditioning pad comprises moving the
conditioning pad across different portions of the pad surface of
the planarizing pad while rotating the planarizing pad.
6. The method of claim 5, wherein moving the conditioning pad
across different portions of the pad surface of the planarizing pad
while rotating the planarizing pad comprises varying the dwell time
of the conditioning pad at the different portions of the pad
surface.
7. The method of claim 6, wherein varying the dwell time of the
conditioning pad at the different portions of the pad surface
comprises making a dwell time of the conditioning pad at the center
of the planarizing pad shorter than a dwell time of the
conditioning pad at an edge of the planarizing pad.
8. The method of claim 1, wherein conditioning a pad surface of a
planarizing pad comprises distributing a solvent formulated to
remove the partially solidified fill material of the planarizing
pad using a conditioning pad.
9. The method of claim 8, wherein distributing a solvent formulated
to remove the partially solidified fill material of the planarizing
pad using a conditioning pad comprises uniformly applying the
solvent across the pad surface of the planarizing pad using the
conditioning pad.
10. The method of claim 8, wherein distributing a solvent
formulated to remove the partially solidified fill material of the
planarizing pad using a conditioning pad comprises: applying the
solvent onto the pad surface of the planarizing pad using a
separate solvent delivery system; and contacting the solvent
applied onto the pad surface with the conditioning pad.
11. The method of claim 8, wherein distributing a solvent
formulated to remove the partially solidified fill material of the
planarizing pad using a conditioning pad comprises delivering the
solvent onto the pad surface of the planarizing pad using the
conditioning pad.
12. The method of claim 11, wherein delivering the solvent onto the
pad surface of the planarizing pad using the conditioning pad
comprises delivering the solvent onto the pad surface of the
planarizing pad through nozzles on the conditioning pad.
13. The method of claim 8, wherein removing a portion of the
partially solidified fill material from the openings comprises
removing the portion of the partially solidified fill material
using the solvent.
14. The method of claim 1, wherein solidifying another portion of
the partially solidified fill material comprises curing a portion
of the flowable and curable portion of the partially solidified
fill material.
15. A method of conditioning a planarizing pad, comprising:
contacting a planarizing pad with a conditioning pad, the
planarizing pad comprising: a pad structure comprising: a pad
material comprising the pad surface; and openings extending from
the pad surface into the pad material, a depth of the openings less
than a thickness of the pad material; and a partially solidified
fill material within the openings and comprising a hardened portion
overlying a liquid portion; and distributing a solvent for removing
the partially solidified fill material of the planarizing pad onto
the pad surface using the conditioning pad.
16. The method of claim 15, wherein contacting a planarizing pad
with a conditioning pad comprises contacting different portions of
the pad surface of the planarizing pad with the conditioning pad at
different times.
17. The method of claim 16, wherein contacting different portions
of the pad surface of the planarizing pad with the conditioning pad
at different times comprises moving the conditioning pad across the
pad surface of the planarizing pad.
18. The method of claim 15, wherein distributing a solvent for
removing the partially solidified fill material of the planarizing
pad onto the pad surface using the conditioning pad comprises
delivering the solvent onto the pad surface using the conditioning
pad.
19. The method of claim 15, wherein distributing a solvent for
removing the partially solidified fill material of the planarizing
pad onto the pad surface comprises simultaneously contacting the
planarizing pad with the conditioning pad and distributing the
solvent onto the pad surface with the conditioning pad.
20. A method of conditioning a planarizing pad, comprising
contacting the planarizing pad with a conditioning pad to remove a
hardened portion of a fill material within openings in a pad
structure of the planarizing pad and expose a liquid portion of the
fill material within the openings in the pad structure.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/469,524, filed May 11, 2012, pending, which is a
divisional of U.S. patent application Ser. No. 11/400,707, filed
Apr. 6, 2006, now U.S. Pat. No. 8,192,257, issued Jun. 5, 2012, the
disclosure of each of which is hereby incorporated herein in its
entirety by this reference.
FIELD OF THE INVENTION
[0002] The invention relates generally to semiconductor processing
methods, and, more particularly, to processing pads used to polish
and/or planarize workpiece substrates during the manufacture of a
semiconductor device, and to apparatus and methods that utilize the
pads.
BACKGROUND OF THE INVENTION
[0003] Chemical-mechanical polishing and chemical-mechanical
planarization processes, both of which are referred to herein as
"CMP" processes, are abrasive techniques that typically include the
use of a combination of chemical and mechanical agents to
planarize, or otherwise remove material from a surface of a
micro-device workpiece (e.g., wafers or other substrates) in the
fabrication of micro-electronic devices and other products. A
planarizing or polishing pad ("CMP pad") is a primary component of
a CMP system. The CMP pad is used with a chemical solution along
with abrasives, which may be present in the solution as a slurry or
fixed within the pad itself, to mechanically remove material from
the workpiece surface.
[0004] FIG. 1 illustrates a conventional chemical-mechanical
planarization (CMP) apparatus 10 with a circular table or platen
12, a carrier assembly 14, and a CMP pad 16. The planarizing
apparatus 10 can have an under-pad or subpad 17 attached to a
surface of the platen 12 for supporting the CMP pad 16. A
drive-assembly 18 rotates the platen 12 (indicated by arrow "A")
and/or reciprocates the platen 12 back and forth (indicated by
arrow "B"), and the motion provides continuous movement of the CMP
pad 16 relative to a workpiece 20 (e.g., a wafer) secured onto a
substrate holder or carrier 22. In the illustrated embodiment, an
actuator assembly 24 is coupled to the carrier 22 to provide axial
and/or rotational motion to the carrier 22 as indicated,
respectively, by arrows "C" and "D". Also as shown, the carrier 22
is coupled by an arm 28 to an actuator 26 that rotates (indicated
by arrow "E") to "sweep" the carrier 22 along a path across the
planarizing surface 30 of the CMP pad 16. Although not shown, the
carrier 22 can also be a weighted, free-floating disk that slides
over the CMP pad 16. Several nozzles 32 attached to the carrier 22
dispense a planarizing solution 34 onto the surface 30 of the CMP
pad 16. In FIG. 2, another embodiment of a typical CMP processing
apparatus 10' is shown with a delivery system 36 having an arm 38
with a nozzle 32 for delivery of a slurry or planarizing solution
34 over the surface 30 of the CMP pad 16 during a planarizing
operation, and nozzles 39 for a high-pressure DI rinse to clean the
CMP pad 16.
[0005] In operation, the workpiece 20 and/or the CMP pad 16 are
moved relative to one another allowing abrasive particles in the
pad or slurry to mechanically remove material from the surface of
the workpiece 20, and reactive chemicals of the planarizing
solution 34 on the surface 30 of the CMP pad 16 to chemically
remove the material. This action results in wear of the planarizing
surface 30 of the CMP pad 16.
[0006] Conventional CMP pads are round or disk-shaped, planar, and
have larger dimensions than the workpiece substrate. CMP pads are
typically fabricated by forming the pad material into large cakes
that are subsequently skived, or sliced, to a desired thickness, or
by individually molding the pad. Pads can also be produced as
individually molded or with abrasives embedded in the pad (i.e.,
fixed abrasive). The condition of the planarizing surface of the
CMP pad is one variable affecting the polishing rate and uniformity
of the polished surface of the workpiece substrate.
[0007] As shown in FIGS. 3 and 4, CMP pads 16 have a thickness "T"
and a planarizing surface 30 (see FIGS. 1 and 2). CMP processes use
pads that typically include openings 40 (e.g., grooves, channels,
perforations) having different grooving styles to improve process
performance, which in the illustrated embodiment are in the form of
grooves. The depth "D", width "W", and pitch "P" (i.e., distance
between sidewalls or lands 41 of the grooves, etc.) of the openings
40 (e.g., grooves) affect the wafer to pad contact area and slurry
transport across the wafer surface. This, in turn, affects the
uniformity of the planarized surface of the workpiece, the
planarizing or polishing rate and capabilities, and defects in the
workpiece surface.
[0008] Most CMP pads are initially received from the manufacturer
with a hydrophobic, non-planar surface. Before use, the planarizing
surface of the CMP pad typically undergoes a conditioning process
to planarize and abrade (roughen) the surface so that effective
planarization of the workpiece surface can be achieved. Typically,
a hard CMP pad is conditioned using a rough or abrasive pad, such
as a diamond or diamond-on-metal conditioning stone or pad. In some
operations, the planarizing pad is removed from the platen and
placed on a separate conditioning machine.
[0009] The planarizing apparatus 10 illustrated in FIG. 1 includes
a second carrier assembly 42 that includes an actuator assembly 44
coupled to a carrier 46 and to an arm 48, which can be actuated to
move the carrier 46 axially (indicated by arrow "F") and/or to
rotate the carrier 46 (indicated by arrow "G") to engage the
conditioning surface 50 of a conditioner or conditioning medium 52
against the planarizing surface 30 of the CMP pad 16. Exemplary
conditioner mediums 52 include, but are not limited to, pads,
diamond brushes, and nylon brushes. The second carrier assembly 42
can include an actuator 54 that operates to rotate the arm 48
(indicated by arrow "H") to move or sweep the conditioning pad 52
in an arcuate sweep path against the planarizing surface 30 of the
CMP pad 16 between processing cycles. The conditioning pad 52
abrades the surface 30 of the CMP pad 16 to planarize it, which
prevents glazing of the pad surface and provides a fresh surface
for polishing.
[0010] The condition of the planarizing surface of the CMP pad also
changes over time from the collection of residual matter on the
planarizing surface of the pad during the CMP operation, which can
glaze over sections of the pad surface. The workpieces can also
wear depressions into the surface of the CMP pad, resulting in a
non-planar processing surface. Typically, a pad is also conditioned
after processing of a number of workpieces to remove slurry residue
and eliminate surface irregularities (e.g., protrusions,
depressions), and restore the surface texture of the pad to a
desired condition for planarizing additional workpieces.
[0011] Referring to FIGS. 4 and 5, wear and conditioning of the CMP
pad 16 leads to a decrease in the initial depth D.sub.1 of the
openings (e.g., grooves) to a reduced depth D.sub.2, which can
affect slurry flow dynamics and affects the useful wear life of the
pad. For example, during processing, the flow of solution (slurry)
across the pad results in abrasive particles of the slurry settling
within the grooves of the processing surface of the pad. Over
multiple applications, comparatively fewer particles settle into
the grooves as the grooves become shallower, which is accompanied
by an increasing amount of abrasive particles being present on the
surface of the pad. This effect alters slurry efficiency and polish
dynamics with respect to later-processed workpieces. Thus, a
gradual reduction of the groove depth of a pad can affect the rate
and uniformity of the polishing process over time, which can
adversely impact later planarized workpieces. In practice, the
number of device polishings for any given pad is tracked and the
pad is then replaced after an experimentally determined number of
cycles, generally before the pad is completely worn out or would
damage the substrate being polished. This is also true in the case
of pads with embedded abrasives in the form of posts standing up.
The posts with abrasives tend to wear during polishing and
conditioning.
[0012] One factor determining the life span of a CMP pad (i.e., the
number of wafers processed per pad) is the depth "D" of the
openings (e.g., grooves) in the CMP pad. For example, if a
particular CMP process requires polishing using a pad having a
shallow groove structure with the depth D.sub.1 of the grooves at
about 250 .mu.m (about 10 mils) with a pad wear of about 0.25
.mu.m/wafer (about 0.01 mil/wafer), with a continuing reduction in
the groove depth to D.sub.2 over time (and an associated reduction
in pad thickness to T.sub.2), the life of the pad will be only
about 600-800 wafers processed. With a pad having a standard
thickness T.sub.1 of about 50-80 mils (about 1.3-2 mm), the pad
should be capable of processing about 6000-8000 wafers with deeper
initial grooving. Thus, although required by process
specifications, the use of shallow grooves results in underuse of
the pad and loss of valuable pad life, as well as the loss of
operator time due to the need to repeatedly shut down the CMP
apparatus to continually replace the CMP pad.
[0013] In manufacturing a pad, the initial depth D.sub.1 of the
openings (e.g., grooves) is machined to a specified depth into the
pad thickness T.sub.1, depending on the process requirements.
However, there are also certain constraints on how deep the grooves
can be formed into the body of the pad.
[0014] For example, there is some amount of movement of the lands
41 of the grooves 40 on the CMP pad 16 during a processing
operation from the pressure applied by the contact and downforce of
the workpiece onto the surface of the CMP pad 16. Typically, the
initial depth (D.sub.1) of the openings 40 is shallow extending
into only about 30% to 40% of the total pad thickness (T.sub.1) in
order to provide a rigid and immovable pad surface for providing an
acceptable planarizing effect. Consequently, about 60% to 70% of
the pad thickness is unused.
[0015] However, forming the openings 40 (e.g., grooves) deeper into
the CMP pad 16 will result in shearing of the lands 41 of the
openings 40 when the CMP pad 16 is put into contact with a wafer,
rather than the lands 41 maintaining a relatively stiff, vertical
stance due to a lack of supporting material adjacent to the lands
41. In addition, deeper grooves without any support can also cause
sidewall collapse due to lack of stability and the viscoelastic
nature of the pad materials. This limits the initial depth D.sub.1
of the openings 40 (e.g., grooves) within the CMP pad 16.
[0016] In addition, deep grooves present pad cleaning challenges.
The slurry particles and polishing debris tend to collect in the
grooves. As shown in FIG. 2, high-pressure DI rinse from the arm 38
using nozzles 32 is delivered to the CMP pad 16 between wafers to
clean polishing debris from the CMP pad 16. If the pad grooves are
significantly deep, it poses challenges to pad cleaning. The debris
that collects in the grooves can lead to defects on the polishing
substrate (wafer) if not cleaned properly. Without properly
controlled pad groove depth, it is difficult to clean the pads.
[0017] Therefore, it would be desirable to provide a CMP pad and
process of planarizing a workpiece that overcomes such
problems.
SUMMARY OF THE INVENTION
[0018] The present invention is directed to processing pads for
mechanical and/or chemical-mechanical planarization or polishing of
substrates in the fabrication of microelectronic devices, methods
for making the pads, and methods and apparatus that utilize the
processing pads.
[0019] In one aspect, the invention provides a processing pad in
which openings (e.g., grooves, perforations, etc.) extending from
the abrading surface of the pad are partially filled with a solid
fill material that can be preferentially dissolved or otherwise
removed from the openings in a controlled manner. Over multiple
applications of the pad in a planarizing operation, as the
thickness of the pad decreases due to use and abrasive action, the
fill is maintained within the openings at a set distance from the
abrading surface of the pad by removing the fill by application of
a composition (different than a planarizing solution) selectively
relative to the pad material, and/or by abrasive action.
[0020] The invention allows the fabrication of openings into a pad
to up to 80% of the initial pad thickness, thus utilizing more of
the pad thickness and extending the life of a pad to an increased
number of applications relative to a standard processing pad. The
presence of the fill material within the openings during a
planarizing operation supports the lands (sidewalls) of the
openings to prevent bending or shearing from pressures on the
abrading surface of the pad by a substrate. The fill material can
be provided in a solid form throughout its depth within the
opening, or as a flowable (and curable) form with an overlying skin
layer. A sufficient portion of the fill is maintained in the
openings over the life of the pad to support the lands and to
provide the required openings according to specifications of the
processing operation at hand.
[0021] In one embodiment of a planarizing pad according to the
invention, the fill material is composed of a polymeric material
having a different chemical make-up than the pad, for example, a
polymeric resist (e.g., a novolac resin, a diazonaphthaquinone,
etc.). Exemplary compositions that can be applied to selectively
dissolve the polymeric resist material within the openings in the
processing pad include aqueous mixtures of hydrogen
peroxide/sulfuric acid, an inorganic fluorine/organic acid, and
ozonated water/acetic acid, and ammonium hydroxide solutions.
[0022] In another embodiment, the openings of the planarizing pad
are filled with a material comprising water-soluble particles such
as glucose, fructose, and other high molecular weight sugars,
within a water-soluble binder (e.g., a calcium-based binder), which
can be dissolved, for example, using an organic acid (e.g., citric
acid, ascorbic acid, etc.), selectively relative to the pad
material. Additional suitable water-soluble particles include
water-soluble salts such as halide salts, and water-soluble gums or
resins, for example, polyvinyl alcohol, and the like.
[0023] In another aspect, the invention provides processing methods
for forming a planarizing pad. In one embodiment, the method
includes filling openings in a planarizing pad to an about set
distance from the pad surface with a flowable material and allowing
the flowable material to solidify to form a fill, the fill being
dissolvable upon contact with a composition selectively relative to
the pad material. In another embodiment, the openings can be filled
and excess fill material can be removed to a set distance from the
pad surface, for example, by applying a composition to selectively
dissolve the fill relative to the pad material, and/or by a buffing
or an abrading process. In yet another embodiment of a pad
fabricating method, openings are formed in a processing pad to up
to about 80% of the pad thickness, with a depth of at least about
50% of the pad thickness being preferred, and then filled with a
flowable fill material. The openings can be filled, for example, by
spinning a liquid material over the surface of the pad, or other
method. The fill material can be hardened throughout, or cured to
form a skin layer over a flowable underlayer.
[0024] In yet another aspect, the invention provides methods of
planarizing a substrate. In one embodiment, the method comprises
planarizing substrates by contact with the abrading surface of a
pad according to the invention, and applying a composition to the
surface of the pad to selectively remove a portion of the fill
within the openings in the pad relative to the pad material to the
about set distance from the pad surface. The steps of planarizing
and applying the composition to remove additional fill from the pad
openings can be repeated to process multiple substrates. In
embodiments of the method utilizing a fill composed of a skin layer
over a flowable material, after removal of fill from the openings,
a portion of the fill can be cured or otherwise hardened to re-form
the skin layer, and the pad continued to be used for planarizing
additional substrates. In another embodiment, after planarizing the
substrate(s), the abrasive surface of the pad can be conditioned,
and the composition applied to the pad surface either during or
subsequent to the conditioning step to remove fill from the
openings.
[0025] In a further aspect, the invention provides systems for
planarizing or polishing a workpiece substrate. An embodiment of a
system according to the invention includes a planarizing or
polishing apparatus comprising a processing pad according to the
invention. In another embodiment, the system includes a substrate
holder, a planarizing pad according to the invention, an actuator
operable to move the workpiece substrate relative to the abrading
surface of the planarizing pad, a source of a composition
formulated to selectively dissolve the fill within the openings in
the planarizing pad, and a dispenser for delivering the composition
onto the abrading surface of the planarizing pad. The system can
further include a carrier for a conditioning pad, and an actuator
operable to move the conditioning pad relative to the abrading
surface of the planarizing pad.
[0026] The dispenser for the composition can comprise, for example,
spray elements spaced along a support connected to an actuator
operable to move the support across the abrading surface of the
pad. The spray elements can be configured to provide vertical
and/or angled delivery of the composition onto the pad. In another
embodiment, the dispenser can be situated on the substrate holder,
and optionally be configured to deliver a planarizing solution onto
the pad surface. In a further embodiment, the dispenser can be
mounted on the carrier for the conditioning pad.
[0027] Yet another aspect of the invention is a conditioning system
for a planarizing pad. An embodiment of a system adapted to
condition an abrading surface of a planarizing pad includes a
support for the planarizing pad, a carrier for supporting a
conditioning pad, a mechanism adapted to move the conditioning pad
in contact with the abrading surface of the planarizing pad, a
source of a composition for dissolving the fill material within the
pad openings, and a dispenser for delivering the composition onto
the abrading surface of the pad.
[0028] The present invention advantageously provides a processing
pad in which a constant groove depth can be maintained over
multiple substrate polishings and conditionings of the pad surface,
which advantageously improves process stability and significantly
increases pad life. By keeping the groove depth to an optimum depth
over multiple planarizing and conditioning cycles and the life of
the pad, the slurry and planarizing dynamics remain about constant
because the amount of abrasive particles that settle in the grooves
and are present on the pad surface are maintained at an about
constant level. This also improves slurry efficiency in a
planarizing operation over multiple cycles of pad use and
reconditioning. The invention eliminates process variations through
the life of the pad due to changing groove depths.
[0029] The technique described herein to maintain a constant groove
depth (opening depth) and/or constant height of pad lower areas
from the polishing surface in a processing pad is compatible with
current pad manufacturing techniques and practices. The present
process provides flexibility to readily utilize processing pads
having differing groove depths without compromising the integrity
or life of the pad. Also, by maximizing the useful life of the
polishing pad, fewer shutdowns are required, throughput and yield
are increased, and operation downtime is minimized. In addition, by
having properly controlled pad groove depth using the present
invention, it is easier to clean the pads.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Preferred embodiments of the invention are described below
with reference to the following accompanying drawings, which are
for illustrative purposes only. Throughout the following views,
reference numerals will be used in the drawings, and the same
reference numerals will be used throughout the several views and in
the description to indicate same or like parts.
[0031] FIG. 1 is a diagrammatic, elevational, cross-sectional view
of an embodiment of a prior art planarizing apparatus.
[0032] FIG. 2 is a diagrammatic, isometric view of a prior art set
up of another embodiment of a tool for performing CMP
processing.
[0033] FIG. 3 is a diagrammatic, isometric view of an embodiment of
a prior art pad for planarizing a workpiece.
[0034] FIGS. 4 and 5 are diagrammatic, elevational, cross-sectional
views of the prior art pad shown in FIG. 3, taken along line 4-4.
FIG. 4 shows the initial pad, and FIG. 5 shows the pad at a
subsequent processing step.
[0035] FIG. 6 is a diagrammatic, elevational, cross-sectional view
of an embodiment of a CMP pad in accordance with the invention at
an initial processing stage.
[0036] FIGS. 7 through 13 are diagrammatic, elevational,
cross-sectional views of the FIG. 6 CMP pad at sequential
processing steps subsequent to that of FIG. 6 according to an
embodiment of the method of the invention. FIG. 7A is a
diagrammatic, elevational, cross-sectional view of a CMP pad
according to another embodiment of the processing step depicted in
FIG. 7. FIG. 9A is a diagrammatic, elevational, cross-sectional
view of a CMP pad according to another embodiment of the processing
step depicted in FIG. 9.
[0037] FIG. 14 is a diagrammatic, isometric view of an embodiment
of a conditioning apparatus according to the invention, having a
high-pressure spray bar system.
[0038] FIG. 15 is a diagrammatic, top view of another embodiment of
a conditioning apparatus according to the invention.
[0039] FIG. 16 is a diagrammatic, isometric view of the
conditioning pad depicted in the apparatus of FIG. 15.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The invention is directed to planarizing pads, and methods
of utilizing the planarizing pads in a mechanical and/or
chemical-mechanical planarization of micro-device workpieces.
[0041] The invention will be described generally with reference to
the drawings for the purpose of illustrating the present preferred
embodiments only and not for purposes of limiting the same. Several
of the figures illustrate processing steps in the fabrication and
use of a planarizing pad in accordance with the present invention.
It should be readily apparent that the processing steps are only a
portion of the entire fabrication process.
[0042] In the context of the current application, the terms
"semiconductor substrate," "semiconductive substrate,"
"semiconductive wafer fragment," "wafer fragment," or "wafer" will
be understood to mean any construction comprising semiconductor
material including, but not limited to, bulk semiconductive
materials such as a semiconductor wafer (either alone or in
assemblies comprising other materials thereon), and semiconductive
material layers (either alone or in assemblies comprising other
materials). The term "substrate" refers to any supporting structure
including, but not limited to, the semiconductive substrates, wafer
fragments or wafers described above. The terms "micro-device
workpiece" and "workpiece" are understood to include a variety of
substrates in or on which micro-electronic devices,
micro-mechanical devices, data storage elements, and other features
are fabricated. For example, workpieces can be semiconductor
wafers, glass substrates, dielectric or insulated substrates, and
metal-containing substrates, among others. The terms
"planarization" and "planarizing" refer to the removal of material
from a surface by chemical-mechanical or mechanical planarization
or polishing). The terms "chemical-mechanical polishing" and "CMP"
refer to a dual mechanism having both chemical and mechanical
components to remove material, as in wafer polishing. The terms
"conditioning pad" and "conditioning stone" may encompass any
structure suitable for abrading or otherwise conditioning a
planarizing pad, including fixed diamond media, for example.
[0043] The following description with reference to the figures
provides an illustrative example in the fabrication of a
planarizing pad (CMP pad) according to the invention, and methods
of its use. Such description is only for illustrative purposes and
the present invention can be utilized to provide other planarizing
pads in other systems. The present invention is not limited to the
described illustrative planarizing pads. The invention can also be
applied using standard, commercially available planarizing pads,
which can be obtained from a variety of sources.
[0044] Steps in an embodiment of a method for fabricating a
planarizing pad 58 according to an embodiment of the invention are
illustrated in FIGS. 6 through 13. The illustrated example is in
the fabrication of a planarizing pad 58 in which the illustrated
openings 60 are grooves in concentric circles (e.g., K-groove
configuration) on a pad surface 66. The example is not meant to be
limiting and the description applies to other openings (e.g.,
perforations, combination of grooves and perforations, etc.) that
are formed in a planarizing pad and can be filled with the
described fill material.
[0045] The CMP pads of any of the embodiments of the invention can
be fabricated using a conventional pad material, for example, a
thermoplastic polyurethane, polyvinyl, nylon,
polymethylmethacrylate, polytetrafluoroethylene, natural and
synthetic resins, among others, and can be filled or unfilled. The
CMP pad can be produced by conventional processes, for example, but
not limited to, casting, molding (injection molding, blow molding,
etc.), sintering, and extrusion.
[0046] The CMP pad can be fabricated without abrasive particles
embedded therein, to be used with a slurry planarization
composition that includes abrasive particles. The CMP pad can also
be in the form of an abrasive polishing pad ("fixed-abrasive pad")
that is fabricated with abrasive particles fixed in the pad
material, to be used with a planarization composition without
abrasive particles therein.
[0047] The CMP pad 58 can be used in combination with a
compressible subpad (e.g., subpad 17 of FIG. 1) such as a
polyurethane foam or felt subpad, or a harder and less compressible
subpad material, which can be adhesively attached together, or
attached to the platen supporting the CMP pad.
[0048] The initial thickness T.sub.1 of the CMP pad 58 can vary
over a wide range. Typically, a CMP pad will have a thickness range
of about 20-200 mils (0.5-5 mm), more typically about 50-120 mils
(about 0.5-3 mm), and more typically about 80-100 mils (about 2-2.5
mm) total thickness.
[0049] In a conventional pad fabrication process, openings 60 into
the pad 58 are initially formed during fabrication or machined into
a formed pad on a lathe or other suitable device. The openings 60
can be any style as desired, and are typically in the form of
grooves, channels, and/or perforations extending into the pad in a
desirable pattern. Exemplary configurations include concentric
circles, spirals, X-Y cross-hatch patterns, K-grooves, and
K-groove/X-Y groove combinations, for example, and can be
continuous or non-continuous in connectivity. In the illustrated
example, the openings 60 are in the form of grooves, and as shown
in FIG. 6, have an initial depth "D.sub.1", width "W", and a pitch
"P" (i.e., distance between openings), all of which affect the CMP
operation.
[0050] In a conventional CMP pad 16 (FIG. 4), the initial depth
D.sub.1 of the grooves 40 is about 30% to 50% of the initial pad
thickness T.sub.1. For example, with a grooved pad 16 having an
initial thickness T.sub.1 of about 80 mils (about 2 mm), the
initial depth D.sub.1 of the grooves 40 is typically about 30-50
mils (about 0.75-1.25 mm). Thus about 40% to 60% of the total
thickness T.sub.1 of the CMP pad 16 is not utilized.
[0051] The inventive planarizing pad 58 differs from a conventional
pad 16 in that the grooves 60 (or other openings) can be initially
formed to a greater depth, which contributes to a longer life span
(i.e., maximum number of wafers processed per pad) of the pad
58.
[0052] The present invention facilitates the initial formation of
deep grooves 60 (or other openings) into the pad 58, which initial
depth D.sub.1 can be up to about 80% of the initial pad thickness
T.sub.1. For example, with a grooved pad 58 having an initial
thickness T.sub.1 of about 80 mils (about 2 mm), the grooves 60 can
be formed to an initial depth D.sub.1 of about 60 mils (about 1.5
mm) deep, or 75% of the pad thickness T.sub.1. In a conventional
pad 16, such a construction could lead to collapsing of lands or
groove sidewalls during planarization. However, in the inventive
pad 58, a fill within the openings 60 supports lands 56 of the
grooves 60, and allows the pad 58 to be worked longer, resulting in
fewer equipment changes on the CMP tool and quality control
testing, among other advantages. In preferred embodiments of a
planarizing pad according to the invention, the initial depth of
the openings (e.g., grooves) are about 50% to 80% of the initial
pad thickness T.sub.1, more preferably about 60% to 80% of pad
thickness T.sub.1, more preferably about 70% to 80% of pad
thickness T.sub.1, and more preferably about 80% of pad thickness
T.sub.1.
[0053] According to the invention, a portion D.sub.x of the grooves
60 (or other openings) are filled with a solid fill material 62
such that only an upper segment D.sub.y of the opening 60 is
exposed. As such, a surface 64 of the fill material 62 within the
opening is at a preset distance (D.sub.y) from the pad surface 66,
which, in effect, reduces the "working depth" of the opening 60. As
an example, about 90% of the initial depth D.sub.1 of the groove 60
can be filled with about 10% of the groove 60 (depth) exposed. Any
portion or ratio of the openings can be filled as desired according
to the process requirements. Thus, the fill reduces the exposed
portion of the openings from the initial depth D.sub.1 (or
D.sub.y+D.sub.x) to depth D.sub.y, thus altering the effective or
operative depth of the openings to provide a "working opening"
(e.g., "working groove") having the desired or predetermined (set)
opening depth D.sub.y for a particular planarization operation
without compromising on pad stability or life time.
[0054] A suitable fill material 62 will at least partially solidify
(e.g., cure) within the openings 60 to a relatively hard matrix,
and be selectively removed from the grooves 60 relative to the pad
material by chemical and/or mechanical removal, for example, by
application of a suitable solvent to selectively dissolve or
solubilize the material and/or by buffing.
[0055] The fill material 62 can be applied by any suitable process
such that the material will deposit and/or flow into the openings
60 including, for example, spin-on processes, deposition processes
(e.g., a chemical vapor deposition (CVD)). In another example, the
fill material 62 can be in the form of a paste that can be
extruded, laminated, or otherwise coated onto the pad surface 66
and made to flow into the grooves 60, for example, through heating.
The fill can then be hardened to a limited depth or throughout its
thickness by a process appropriate to the nature of the fill, for
example, by curing, cooling, heating, or other suitable
technique.
[0056] Exemplary fill materials include, for example, a polymer
material such as a resist material, which will dissolve selectively
relative to the pad material by application of a solvent, and is
chemically and reactively different than the pad material.
Exemplary photoresists comprise an organic polymeric material, and
include novolac resins and diazonaphthaquinone (DNQ). An organic
polymer photoresist fill material can be wet etched by applying,
for example, an aqueous mixture of hydrogen peroxide and sulfuric
acid (H.sub.2SO.sub.4/H.sub.2O.sub.2), an aqueous mixture of an
inorganic fluorine (e.g., hydrofluoric acid (HF), ammonium fluoride
(NH.sub.4F)) and an organic acid (e.g., citric acid, acetic acid),
an ammonium hydroxide solution (e.g., tetramethyl ammonium
hydroxide), ozonated DI water with acetic acid, and the like.
[0057] Another example of a fill is a material comprising
water-soluble inorganic or organic particles such as an organic
salt or a soluble polymer particle, dispersed in a water-soluble
binder. Examples of water-soluble particles include high molecular
weight sugars such as glucose, fructose, mannose, sucrose, lactose,
maltose, dextrose, and starch; a soluble salt such as an inorganic
halide salt, for example, sodium iodide (NaI), potassium chloride
(KCl), potassium bromide (KBr), and ammonium fluoride (NH.sub.4F);
water-soluble gums or resins such as polyvinyl alcohol, polyvinyl
acetate, pectin, polyvinyl pyrrolidone, hydroxyethyl cellulose,
methyl cellulose, hydropropylmethyl cellulose, carboxymethyl
cellulose, hydroxypropyl cellulose, polyacrylic acid,
polyacrylamide, polyethylene glycol, polyhydroxyether acrylate,
maleic acid copolymer, and polyurethane; among others. An average
particle size diameter of the water-soluble particles may range
between about 0.05-500 .mu.m. Examples of water-soluble binders
include calcium-based binders such as calcium acetate and calcium
carbonate that will encapsulate the fill particles and break down
by the application of an appropriate solvent, for example, an
organic acid such as citric acid, tartaric acid, ascorbic acid,
acetic acid, gluconic acid, malic acid, malonic acid, oxalic acid,
succinic acid, gallic acid, formic acid, propionic acid, n-butyric
acid, isobutyric acid, benzoic acid, and the like. Generally, the
particles can be mixed with a binder at between about 0.5-70 wt
%.
[0058] The fill material 62 can be applied to fill or partially
fill the openings 60. As illustrated in FIG. 7, the fill material
62 has been applied such that excess material (overage) outside the
openings 60 overlies the surface 66 of the pad 58. Such excess
material can be removed from the pad surface 66 by a mechanical
and/or chemical process, for example, by buffing with a
conditioning pad, for example, and/or applying a solvent (e.g., a
liquid) to solubilize the fill material 62, to expose the pad
surface 66 with the fill material 62 remaining only in the openings
60, as shown in FIG. 8.
[0059] Referring to FIG. 9, a portion of the fill material 62 is
removed as needed from the openings 60 to the predetermined depth
D.sub.y according to process requirements. The remaining fill
material 62 within the grooves 60 having depth D.sub.x provides
support to the lands 56 and prevents collapse of the grooved
surface of the pad 58. The fill material 62 can be removed by a
suitable process, for example, by buffing and/or applying a solvent
that will selectively remove the fill material 62 as desired
relative to the pad material. Suitable solvents are those that will
etch or dissolve (solubilize) the fill material 62 at a
controllable rate to avoid removal of an excess amount of fill from
the openings. The solvent is also different from the chemistry of
the planarizing solution used in the particular application. The
solvent chemistry required to dissolve the fill material 62 can be
water-based (aqueous) or based on organic chemistries, depending on
the chemistry of the fill material.
[0060] In another embodiment illustrated in FIG. 7A, after applying
a liquid fill material 62' over a pad surface 66' and into the
openings 60', fill material 62' can be partially solidified or
hardened to form a skin-like surface layer 68', for example, about
1-2 mils thick (about 0.025 mm to 0.052 mm). For example, the pad
58' can be coated with a UV-curable polymer, which can be exposed
to UV light to cure a surface layer 68' on the fill material 62'.
Excess fill material 62' can be removed from the surface 66' of the
pad 58' and from the openings 60' to the desired depth D.sub.y'
(FIG. 9A) by buffing or abrading with a conditioning pad, for
example, and/or by applying an appropriate solvent to solubilize
the fill 62'. Referring still to FIG. 9A, the remaining fill
material 62' within the openings 60' can then be partially
solidified or hardened to form another skin-like surface layer
68.sup.a'. After performing subsequent planarizing steps, the
skin-like surface layer 68.sup.a' and additional underlying fill
material 62' can be removed to the desired depth D.sub.y' within
the openings 60', and the fill can be re-cured or otherwise
hardened to form another skin-like surface layer (similar to
68.sup.a').
[0061] The invention provides the ability to vary the working depth
D.sub.y of the groove according to process requirements. For
example, the pad grooves can be filled to provide an initial
working depth D.sub.y(1) of about 100 .mu.m and, at a later
processing application, the fill can be removed to provide a
working depth D.sub.y(2) of about 700 .mu.m.
[0062] During CMP processing of a workpiece (e.g., see FIG. 1), a
planarizing solution is used that is compatible with the fill
component, such that a minimal amount of the fill is removed from
the pad openings. For example, a solution for planarizing a copper
layer using a CMP process is typically neutral to acidic and
includes an oxidizer (e.g., hydrogen peroxide) to oxidize the
copper and increase the copper removal rate. The fill material
utilized in such application would be compatible with the slurry
solution such that a minimum amount of the fill up to about 1 mil
(0.025 mm) is removed.
[0063] After planarizing, a cleaning solution (e.g., water or other
solution) is typically applied to the pad under pressure to remove
slurry and planarizing debris from the surface of the pad (not
shown).
[0064] During processing on a CMP tool, abrading contact of the CMP
pad 58 with the workpiece surface removes a portion of the land
areas 56 of the grooves 60, thus reducing the thickness of the CMP
pad 58 (to T.sub.2) and the total depth of the grooves 60 (to
D.sub.2), and the depth of the exposed portion of the openings 60
to less than the specified preset depth (i.e., to less than
D.sub.y), as depicted in FIG. 10, which can alter the slurry
dynamics and planarization of the workpiece.
[0065] To reestablish and maintain the depth of the exposed portion
of the openings 60 (and the surface 64 of the fill material 62 from
the pad surface 66) to the preset depth D.sub.y, a portion of the
fill material 62 can be mechanically and/or chemically removed
(FIG. 10, arrows 70) from the openings 60 to the desired depth. The
fill material 62 is preferably etched at an about constant rate in
order to maintain the fill at the desired depth D.sub.y. This
provides an about constant opening depth D.sub.y throughout a CMP
processing operation. By comparison, on a standard pad 16, the
depth of the openings 40 decreases (D.sub.1 to D.sub.2 in FIGS. 4
and 5) during CMP processing due to continuous abrasion and
decreasing height of the lands 41 of the grooves 40.
[0066] The fill removal step (arrows 70, FIG. 10) can be performed
after planarizing step removing a workpiece from the CMP tool, for
example, by buffing the surface 66 of the pad 58 or by wet etching
with an appropriate solvent to selectively remove the fill material
62 to the predetermined depth D.sub.y within the openings 60, as
shown in FIG. 11, thus reducing the total depth of the fill to
D.sub.x2. Additional planarizing and fill removal steps can be
performed, eventually resulting in the structure shown in FIG. 12,
whereby the depth D.sub.x3 of the fill material 62 is about equal
to the preset depth D.sub.y of the "working" groove, and the
remaining fill material 62 in the grooves 60 is removed (FIG.
13).
[0067] A fill-removal solvent 72 is applied so as to assure that
the etching is uniform across the surface 66 of the pad 58. The
solvent can be delivered by any suitable method, for example, using
a solvent delivery system 74 as illustrated in an embodiment of a
CMP apparatus 76 in FIG. 14, as a high-pressure spray bar system
having spray nozzles 78 positioned at intervals along an arm or bar
80 that delivers an appropriate solvent 72 (e.g., water or other
chemistry) while the CMP pad 58 is rotating to ensure uniform
etching of the fill material across the pad surface 66. The spray
bar 80 is connected to a sweep actuator 82 that rotates (indicated
by arrow "F") to sweep the spray bar 80 across the surface 66 of
the CMP pad 58. The nozzles 78 can also be connected to a line for
delivery of a pad cleaning solution. As shown, the spray bar 80 can
also include a nozzle 84 for delivery of a slurry or planarizing
solution 86 onto the pad surface 66.
[0068] Solvent delivery parameters can be varied according to the
nature of the fill material to effectively remove the desired
amount of fill from the openings, including, for example, the
pressure of the spray delivered through the nozzles 76, the angle
of delivery onto the pad 58 (e.g., 90.degree. angle, 45.degree.
angle to the pad, etc.), the duration of solvent application, the
temperature of the solvent, the concentration of the solvent, and
the like. Solvent delivery can also be varied according to the size
of the CMP pad, and the rotational speed of the pad, among other
factors.
[0069] The CMP system 76 illustrated in FIG. 14, also includes a
conditioning assembly 88. During delivery of the fill-removal
chemistry 72, the CMP pad 58 can optionally be conditioned using a
conditioning pad 90, which can be used to distribute the
fill-removal solvent 72 and to apply a downward pressure as needed
such that the solvent 72 is uniformly applied across the surface 66
of the CMP pad 58.
[0070] Referring to FIGS. 15 and 16, in another embodiment of an
apparatus 76' that includes a conditioning assembly 88', the
conditioning pad 90' can be structured to incorporate a delivery
system for the fill-removal solvent 72' through nozzles 92'
connected to a solvent supply source (not shown). The conditioning
pad 90' can be connected to an arm 94' and sweep actuator 96', and
swept or moved across the CMP pad 58' in a conditioning procedure
while delivering the fill-removal solvent 72' onto the pad surface
66'.
[0071] The conditioning pad can be moved over the pad surface at
varying rates to provide a longer dwell or residence time at
different regions of the pad depending on the extent of the fill
removal that is desired and to provide uniformity in the removal of
the fill material from the openings. For example, the system can be
programmed such that the dwell time of the conditioning pad is
about 1% at the center of the pad and about 25% near the edge of a
wafer.
[0072] The fill removal step 70 (FIG. 10) can be automated through
software within the CMP system 76 for performance after a
predetermined number of workpieces (e.g., wafers) have been
processed, for example, after every 10 or 100 wafers, etc.,
depending on the particular CMP process and the rate of change or
deviation of the pad (i.e., the lands) and/or the depth of the
exposed portion of the openings, which can be experimentally
determined.
[0073] The CMP apparatus 76 can also include a monitoring system 98
(FIG. 14) that will alert an operator, for example, when the
thickness and/or uniformity of the wafer or other workpiece is
outside a set specification and acceptable deviation (e.g.,
.+-.2%), and it is time to reestablish the desired depth D.sub.y of
the grooves 60 or other openings. Such monitoring systems are known
in the art, for example, as described in U.S. Pat. Nos. 6,213,845
and 6,872,132 (to Elledge) and commercially available.
[0074] The monitoring system 98 can also comprise a device that
measures groove depth, and when the "working" groove depth is not
within an acceptable deviation (e.g., .+-.2%) of the preset depth
D.sub.y, the fill-removal step 70 (FIG. 10) can be automatically
triggered. Such groove depth measurement systems are known in the
art, for example, as described in U.S. Patent Application
Publication No. 2005/0051267 (to Elledge).
[0075] The etching or removal of the fill material can also be
varied across the surface 66 of the CMP pad 58, for example, from
the center to the edge. This can be achieved, for example, by
changing the concentration of the solvent 72, varying the pressure
of the solvent delivery (e.g., 50 mls/minute in the center of the
wafer to 200 mls/minute near the edge of the wafer), and varying
the angles of the nozzles 78 and spray delivery along the delivery
arm 80 to deliver more solvent along the outer edge of the CMP pad
58 than at the center of the CMP pad 58.
[0076] The elements of the present CMP system are designed for
compatibility such that the fill-removing solvent selectively
removes the fill material and does not react with and is compatible
with the pad material, the planarizing solution selectively removes
the targeted material(s) on the workpiece and does not
substantially remove or react with the fill material (or the pad
material), and the chosen fill material is compatible with the
planarizing solution.
[0077] In compliance with the statute, the invention has been
described in language more or less specific as to structural and
methodical features. It is to be understood, however, that the
invention is not limited to the specific features shown and
described, since the means herein disclosed comprise preferred
forms of putting the invention into effect. The invention is,
therefore, claimed in any of its forms or modifications within the
proper scope of the appended claims appropriately interpreted in
accordance with the doctrine of equivalents.
* * * * *